1. Field of the Invention
The disclosed and claimed concept relates to power pole inverters and, more specifically, to a power pole inverter including a number of arm assemblies, each including a neutral terminal, wherein each neutral terminal is electrically isolated from the ground and a housing assembly.
2. Background Information
Adjustable Speed or Variable Frequency Drives (ASDs or VFDs) are commonly used to operate polyphase AC induction motors at any speed desired by the end user. The advantage of using VFDs include low starting currents, low torque shock on equipment coupled to the driven motor. They also allow sophisticated control of speed and torque profiles as required by end users. VFDs operate by taking either incoming AC or DC power, having a fixed frequency and voltage, and converting it to AC power having a voltage or current with variable amplitude and frequency.
A VFD drive includes a plurality of inverters and a converter which are electrically coupled through electrical buses and physically coupled through their respective modular bases. The inverters may share a common cooling system connected to the respective heat sinks of each component. That is, a VFD is made up of a plurality of inverter modules, which are connected to a converter module to create the VFD, wherein each of the above components is packaged in a relatively small unit having a cooling apparatus. Each of the inverters is made of a modular base, a heat sink or exchanger connected to the base having a plurality of power semiconductor switches, a power supply and a gate driver, thermally coupled thereto, a plurality of capacitors, a plurality of electrical buses connecting the power semiconductor switches to the capacitors, and an insulative medium which encases or covers some or all of the electrically live components, such as the electrical buses. It is further noted that the conductors wrapped around the heat sink, i.e. the conductors were U-shaped.
The inverters are, generally, assembled as follows. The semiconductor switches, power supply, gate driver, and other electrical devices, hereinafter “electrical components,” are coupled to the heat sink or base element. The electrical components are coupled to a bus, or a number of electrical buses. The heat sink, number of electrical buses, and electrical components are then arranged in an open ended housing assembly. The housing assembly may abut the heat exchange assembly. Thus, the housing assembly is open on one end and otherwise encloses the heat sink and electrical components. The electrical devices associated with the Power Pole arm are encapsulated with an insulating potting compound such as, but not limited to, silicone based compound, and the potting compound is cured and forms part of the physical protection. Thus, the number of electrical buses, and electrical components are encased in the potting compound. Alternatively, a minor portion of a component could be exposed. Thus, all, or substantially all, of the components were enclosed.